This invention relates to a seal assembly adapted to be mounted on axle systems and reduction gears of bulldozers and shovel bulldozers or the like for holding lubricating oil therein and preventing foreign matters such as soil and sand etc., from intruding into rotary parts of the bearings thereof.
The conventional seal assembly "A" is mounted, for example, as shown in FIG. 1, between a support shaft "a" and a lower rotary wheel "b" rotatably fitted on the support shaft from the outside thereof, and is of a construction wherein seal surfaces "d" of a pair of seal rings "c", "c" are abutted to each other with a pair of elastomeric retainer members mounted thereon whereby forming a seal surface "f" as shown in FIG. 2.
In such type of seal assembly, when it is put to use for a long period of time, its seal surface "d" tends to be worn by erosion from the outer peripheral portion thereof due to intrusion of soil and sand therein thereby reducing the effective width "h" of the seal surface "f" as shown in FIG. 3. When such seal assembly is used further, it is worn successively as illustrated by imaginary lines in FIG. 3 so that the effective width "h" of the seal surface "f" is remarkably reduced. As a result, the seal assembly will lose its sealing effect finally and cause oil leaks.
Further, if the seal surfaces "d" of the above-mentioned seal rings "c" are finished in smooth parallel surfaces, the outer peripheral ends of the seal surfaces "d" tends to form a small opening therebetween when the seal rings "c" are allowed to come into contact with each other with a pair of elastomeric retainer members mounted thereon. In consequence, earth and sand will intrude into the small opening to accelerate the erosion wear of the seal assembly so that the latter will lose its sealing effect in an early stage.
To overcome such difficulties, there has been proposed a seal assembly in which seal surfaces "d" of seal rings "c" are finished by lapping to form a taper respectively, towards the inner peripheral surfaces thereof so that the seal surfaces can tightly engage with each other when they are allowed to about to each other through elastomeric retainer members mounted thereon.
This construction is, however, disadvantageous in that the seal surfaces "d" of the seal rings "c" require to be tapered in the order of microns, and so it is very difficult to finish them by lapping.
Further, there has been proposed a seal assembly (U.S. Pat. No. 3,180,648) in which as shown in FIG. 4 the portions "g" below seal surfaces "d" of seal rings "c" are tapered so that wearing part "i" can extend radially in turn with the lapse of time of use. This type of construction is disadvantageous in that since the seal effect is provided by seal surfaces including a considerably large wearing portion "i," coarse particles of foreign matters tend to intrude through the wearing portion "i" into the seal surfaces so that the latter are worn out quickly due to a kind of gauzing action thereby losing their sealing effects very quickly.